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Laptop Chargers

Granz00

Posted 11 September 2008 - 07:21 PM

Granz00

Member

Member

226 posts

Okay, my buddy online seems to have a dead laptop charger. Someone from his work tested it (their IT specialist), and told him that it was dead. The input for the laptop is 110W, and the guy told him that a 90W would work, but it would just charge slower. This sounds kinda fishy to me. Is he right, and is there anything my friend should worry about if using the 90W charger?

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Major Payne

Posted 11 September 2008 - 10:30 PM

Major Payne

Retired Staff

Retired Staff

5,307 posts

I wouldn't trust a lower rated charger as the battery will draw what current it needs to fully charge at the rated charge voltage. The charger is more than likely to overheat or even burn out if the current rating is at least the same as the original. Always best to get an exact replacement or one of better quality if available.

shard92

Posted 12 September 2008 - 12:23 PM

shard92

Member 1K

Member

1,129 posts

look at the amperage.... if it is not supplying enough amps then it's going to burn out.... just like running a big truck on a motor designed for a compact.... it might work but he motor is going to be over worked....

Major Payne

Posted 12 September 2008 - 03:30 PM

On our Dells, that is the case. A 65W adapter will run a 90W computer, just charge the battery slower, if it all.

Using a 115W on a 90W will charge the battery faster, but decrease the life of the battery accordingly.

The charging rate is determined by the actual voltage being applied to the battery. For the same rated voltage rating, but difference in current that can be supplied (115w vs. 90w), the lower power one will run hotter, be subject to burn out (possibly on the promary side) or an incomplete battery charge. The charging battery, depending on the charging circuit (trickle charger, constant current, etc.), will try to take what it needs current-wise. Always best to get the rated battery charger recommended by manufacturer. Both chargers, if of same rated voltage, will charge the battery the same. Again, the lower power one will just run hotter with possible subsequent problems. A lot depends on the charging circuit used to control the charging.

A simple charger works by connecting a constant DC power source to the battery being charged. The simple charger does not alter its output based on time or the charge on the battery. This simplicity means that a simple charger is inexpensive, but there is a tradeoff in quality. Typically, a simple charger takes longer to charge a battery to prevent severe over-charging. Even so, a battery left in a simple charger for too long will be weakened or destroyed due to over-charging.

A trickle charger is a kind of simple charger that charges the battery slowly, at the self-discharge rate. A trickle charger is the slowest kind of battery charger. A battery can be left in a trickle charger indefinitely. Leaving a battery in a trickle charger keeps the battery "topped up" but never over-charges.

The output of a timer charger is terminated after a pre-determined time. Timer chargers were the most common type for high-capacity Ni-Cd cells in the late 1990s for example (low-capacity consumer Ni-Cd cells were typically charged with a simple charger).

Often a timer charger and set of batteries could be bought as a bundle and the charger time was set to suit those batteries. If batteries of lower capacity were charged then they would be overcharged, and if batteries of higher capacity were charged they would be only partly charged. With the trend for battery technology to increase capacity year on year, an old timer charger would only partly charge the newer batteries.

Timer based chargers also had the drawback that charging batteries that were not fully discharged, even if those batteries were of the correct capacity for the particular timed charger, would result in over-charging.

Fast chargers make use of control circuitry in the batteries being charged to rapidly charge the batteries without damaging the cells' elements. Most such chargers have a cooling fan to help keep the temperature of the cells under control. Most are also capable of acting as a standard overnight charger if used with standard NiMH cells that do not have the special control circuitry. Some fast chargers, such as those made by Energizer, can fast-charge any NiMH battery even if it does not have the control circuit.